Background. Aloe contains numerous bioactive compounds which are attributed to have health advantages. Widely used in the cosmetic and pharmaceutical industries, also found its application in the food industry. The antioxidant compounds in aloe may increase the stability and nutritional value of food. The aim of the paper was to evaluate the results of the antioxidant properties of aqueous extract of aloe in model systems.

Material and methods. Analyses were conducted on true aloe (Aloe vera L.). Extraction was run using water at temperature 80–90°C. The level of phenolics was determined spectrophotometric­ally with the Folin-Ciocalteu reagent, using gallic acid as a standard. Antioxidant activity of extract was analysed in relation to linoleic acid, running incubation for 19 h, by scavenging of stable radical DPPH (2,2-diphenyl-1-picrylhydrazyl) and cation radical ABTS (2,2'-azino-bis[3-
-ethylbenzothiazoline-6-sulfonic acid]) and on the basis of metal chelating ability. Recorded results were compared with the activity of BHT (butylated hydroxytoluene).

Results. The total phenolic content of water extract of aloe was 17.85 mg/g d.m. The extract exhibited concentration-dependent DPPH and ABTS radical scavenging activity. The ability was in the range of 4.32–8.87 and 0.58–0.87 mg of trolox per 1 g d.m., respectively. A lower chelating ability of the aloe extract was 1.23 mg EDTA per 1 g d.m. at 20 mg/ml concentration and the higher was 8.76 mg EDTA per 1 g d.m. at 10 mg/ml concentration. The aloe extract reduced levels of the conjugated dienes in the emulsion system. The samples with additions of 0.1–0.5 mg/ml extract contain over 90% less of dienes than control sample. The addition of 0.05 mg/ml and 0.06 mg/ml results in significantly lower (40% and 57%, respectively) activities of the aloe extract.

Conclusions. The extract of aloe showed different antioxidant properties in various model systems. The available literature on the antioxidant potential of aloe is still rather scarce. Due to the complex composition and broad activity of aloe, raw material should be further studied.